Cationic polysaccharides constitute a very useful class of polymers. They are commonly used in a wide variety of industrial applications including papermaking and printing processes, cosmetics, personal care formulations, water treatment, oil drilling fluids, ore treatments, drug delivery systems, detergents, and textiles. They are particularly useful in the chemical field where they are commonly used as complexing agents to bind to negatively charged species, i.e. negatively charged particles or molecules.
Quaternary ammonium derivatized polysaccharides, such as the quaternary ammonium derivatives of guar, starch and cellulose, represent a commonly used family of cationic polysaccharides. These polysaccharides are usually prepared by reacting a polysaccharide with a quaternary amine derivative under alkaline conditions. Typical non-limitative examples of procedures for making cationic polysaccharides are disclosed by Tassett (U.S. Pat. No. 4,464,528), Jarowenko et al. (U.S. Pat. No. 4,281,109), Harding et al. (U.S. Pat. No. 4,505,775), Caesar (U.S. Pat. No. 3,422,087) and Schlack (U.S. Pat. No. 2,131,120).
Guanidine groups constitute strong bases, exhibiting pKa values often exceeding 12. These high pKa values can be attributed to π-electron delocalization of the characteristic C═N linkage (several resonance structures are possible for guanidine groups).
Guanidinium and/or bi-guanidinium groups have been grafted to chitosan as disclosed by Toshio (JP 60-233102), Stockel (U.S. Pat. No. 5,637,681) and Seo et al. (Kobunshi Robunshu, 53 (1), 1996, P 70-76). The amidination and guanidination reactions commonly involve the use of a cyanamide derivative. However, as reported by Elizer et al., polysaccharides comprising O-amidine linkages are unstable. Due the labile nature of the O-amidine linkage, these polysaccharides typically display a shelf-life of only about 24 hours at room temperature, and about 2 days at 0° C.
Payne et al. (WO 04/073034) teach that polysaccharides bearing guanidinium groups are particularly useful for electrochemical deposition on anodes. However, Payne et al. do not teach the absorbent properties of such guanidinated polysaccharides.
Polysaccharides comprising grafted guanylhydrazone groups have been disclosed by Mehltretter (U.S. Pat. No. 3,230,213) and Shima (JP 59-102939). The guanylhydrazone grafted polysaccharides were reported by Shima as possessing absorbent properties. The guanylhydrazone groups were grafted to the polysaccharide by reacting a periodate-oxidized starch with an aminoguanidine derivative. However, due to the inherent unstable nature of imines in aqueous and alkaline environments, guanylhydrazone grafted polysaccharides are not suited as absorbents for liquids.
Arginine modified polysaccharides have been disclosed by Cheng et al. (U.S. Pat. No. 6,159,721), Kurauchi et al. (US 2004/0244706 A1; US 2004/0265435 A1) and Lapidot et al. (US 2004/0229265; WO 00/39139 A1). More specifically, an L-arginine-modified pectin has been disclosed by Cheng et al. However, the enzyme catalyzed amidation reaction is specific to water-soluble polymers having alkoxy and carboxylic acid functionalities, e.g. pectin. An amino-acid ester of cellulose was described by Kurauchi et al. However, Kurauchi et al. do not teach the ester as forming gels, an essential property of absorbent materials for trapping liquids. The polysaccharides as reported by Lapidot et al., were not disclosed as being useful as absorbent materials.
Cationic polysaccharides having superabsorbent properties have been disclosed by Fornasari et al. (U.S. Pat. No. 5,780,616). These polysaccharides, having a degree of substitution (DS) of at least 0.5, are substituted by quaternary ammonium groups, and are cross-linked to a sufficient extent such that they remain insoluble in water. An increase in the number of functional groups in the product was reported as improving the superabsorbent properties.
Resins comprising guanidine groups have found wide spread use as strongly basic anion exchange resins, and have been disclosed by Corte et al., (U.S. Pat. No. 3,856,715) and Matie et al., (Omagiu Raluca Ripan pp. 363-374, 1966). Furthermore, poly(vinylguanidine)-based superabsorbent gels have been disclosed by Mitchell et al. (U.S. Pat. No. 6,087,448). However, this material was not reported as being biodegradable.
Water absorbent materials, such as superabsorbent polymers, can be employed in various applications such as in disposable sanitary products (e.g. diapers, incontinence articles, feminine hygiene products, airlaids and absorbent dressings), household articles, sealing materials, humectants in agricultural products for soil conditioning, anti-condensation coatings, water-storing materials in agriculture/horticulture, and as chemical absorbents. Furthermore, they can be employed in applications related to the transportation of fresh food or seafood, and in food packaging applications.
Superabsorbent polymers can be grouped into the following categories: i) naturally occurring polymers (e.g. starch and other physically modified polysaccharides); ii) semi-synthetic polymers (e.g. carboxyalkylated starch and crosslinked derivatives); and iii) synthetic polymers.
Synthetic water absorbent polymers have experienced rapid development, resulting in diversities and quantities far exceeding those observed for natural and semi-synthetic water absorbent polymers.
Polyacrylates, polyacrylamides, and their copolymers are among the best known synthetic superabsorbent polymers. Acrylic superabsorbent polymers are described in “Modern Superabsorbent Polymer Technology”, Buchholz F. L. and Graham A. T. Eds., Wiley-VCH, New York, 1998.
Crosslinked polyacrylic acids (and corresponding salts) have hitherto been used as water absorbent materials. However, crosslinked polyacrylic acids (and corresponding salts) do not easily biodegrade. Moreover, cross-linked polyacrylic acids are obtained from non-renewable feedstocks, creating provisioning problems.
Semi-synthetic superabsorbent polysaccharide-based grafted polymers are obtained through grafting of an unsaturated monomer (acrylonitrile, acrylic acid, acrylamide) onto starch or, less frequently, cellulose. Such polymers, also called “Super Slurpers”, have shown water absorption ranging from 700 to 5300 g/g for deionized water, and up to 140 g/g in a 0.9% saline solution (weight by weight of NaCl, referred to hereinafter as saline solution) (Ricardo P. O., Water-Absorbent Polymers: A Patent Survey. J. Macromol. Sci., Rev. Macromol. Chem. Phys., 1994, 607-662 (p. 634). Despite their high water absorption, these grafted polysaccharides, prepared by radical polymerization, are known for not being biodegradable and hypoallergenic.
There is a growing interest in the exploitation of natural polymers for commercial applications. Ideally, these natural polymers are derived from renewable sources (e.g. chitin, starch, guar or cellulose), providing for environmentally friendly products. There is a particular interest in chitin, a natural polymer extracted from crustacean shells such as crabs, lobsters, shrimps and insects. It is considered the second most abundant polysaccharide on earth, after cellulose. Chitosan, which is derived from chitin by deacetylation, is structurally similar to cellulose.
Modified starches have also been used as biodegradable absorbent materials as disclosed by Qin et al. (U.S. Pat. Nos. 5,550,189; 5,498,705; and 5,470,964), Besemer et al. (WO 0035504A1; WO 0134656A1; and WO 9929352A1), Chung-Wai et al. (U.S. Pat. Nos. 5,932,017; 6,231,675; and 6,451,121), Shah et al. (U.S. Pat. No. 5,718,770), (Shi et al. U.S. Pat. No. 6,277,186) as well as by Beenackers A. A. C. M. et al. (Carbohydr. Polym., 2001, 45, 219-226). Oligomeric polyethylene glycol crosslinked polysaccharides, in particular polyethylene glycol crosslinked starch, have also been disclosed as useful absorbents by Couture et al. (CA 2,362,006).
The use of biodegradable, glass-like, pregelatinized starch as an absorbent for liquids has been previously disclosed by Huppe et al. (CA 2,308,537). However, this pregelatinized starch was shown to only absorb 8 g/g, which is insufficient to be useful for use in the hygiene industry. In order to improve the absorption capacities of this modified starch, it was mixed with xanthan and guar gums. Moreover, it has also been mixed with sodium carboxymethyl cellulose (CMC). However, the absorption performances remained insufficient to be useful for use in applications requiring a high degree of absorption, such as in baby diapers. The absorption characteristics of this modified starch could be attributed to amylopectin, a high molecular weight polysaccharide component of starch. It was found that amylopectin, when crosslinked, provides for materials having improved absorption characteristics [Thibodeau et al. (CA 2,462,053)]. Furthermore, as disclosed by Bergeron et al. (CA 2,426,478), it was observed that these modified starches could synergistically interact with mannose containing polysaccharides, ionic polysaccharides, gelling proteins or mixtures thereof. These synergistic interactions have been found to be especially useful in formulating absorbent materials. More recently, Berrada et al. (CA 2,483,049) disclosed that phylosilicates, when dispersed in an absorbent polysaccharide matrix, generate a nanocomposite system having excellent absorbent characteristics.
Unfortunately, most modified polysaccharide-based materials do not possess absorptive properties comparable to many of the synthetic, highly-absorptive materials. Moreover, most polysaccharide based materials are based on anionic or neutral polysaccharides, preventing their use in multivalent cationic environments such as drilling fluids and physiological fluids. This in turn has prevented acceptance and widespread use of such modified polysaccharides in absorbent personal care products.
There thus remains a need for modified highly absorbent natural-based polysaccharides suitable for use in personal care products.
The present invention seeks to meet these and other needs.
The present invention refers to a number of documents, the content of which is herein incorporated by reference in their entirety.